The IR studies of the status of Cu⁺ ions in CuZSM-5 CuBeta and in CuMCM-41

The electron donor properties of Cu⁺ and the ability to activate adsorbed molecules by π-back donation of d electrons of Cu⁺ to π* antibonding orbitals of a molecule increases in the order: CuMCM-41 < CuZSM-5 < CuBeta. It was evidenced by IR studies of CO, N₂, and NO adsorption. TPD-IR experiments provided information on heterogeneity of Cu⁺ sites in all the zeolites studied. The experiments on the reduction (in H₂) and oxidation (in air) evidenced that the ability of Cu⁺ to reduction and oxidation depends on zeolite structure. The ability to reduction increased in the order: CuMCM-41 < CuBeta < CuZSM-5, whereas the ability to oxidation increased in the opposite order.